Functionalized elastomer

ABSTRACT

The present invention is directed to a stereoregular functionalized elastomer represented by poly(M1 co M2), wherein the functionalized elastomer comprises a microstructure selected from the group consisting of microstructures having at least 90 percent by weight of monomer residues in trans 1,4-configuration, and microstructures having at least 80 percent by weight of monomer residues in cis 1,4-configuration; wherein M1 is selected from the group consisting of isoprene and 1,3-butadiene; and M2 is of formula 4 
                         
wherein R 6  is a covalent bond, phenylene, a linear or branched alkane diyl group containing 1 to 10 carbon atoms, or a combination of one or more phenylene groups and one or more linear or branched alkane diyl groups containing 1 to 10 carbon atoms; R 7  is hydrogen or a linear or branched alkyl group containing 1 to 10 carbon atoms; X 1  is selected from formulas 5 and 6
 
                         
wherein R 8  and R 9  are independently trialkylsilyl, phenyl or a linear or branched alkyl group containing 1 to 10 carbon atoms, or one of R 8  and R 9  is hydrogen and the other is phenyl or a linear or branched alkyl group containing 1 to 10 carbon atoms, or R 8  and R 9  taken together with the nitrogen atom represent a nitrogen containing heterocyclic group containing from 4 to 12 carbon atoms; and X 2  is a sulfur atom or a structure of formula 7 or 8
 
                         
wherein when X 2  is of formula 8, the S atom of formula 8 is adjacent to the phenyl ring of formula 6 and the N atom of formula 8 is adjacent to R 6 .

BACKGROUND OF THE INVENTION

To produce stereoregular polymers, catalytic insertion polymerization isthe method of choice. Resulting stereoregular poly(1-olefins) andpoly(dienes) are of enormous practical importance. An introduction ofpolar groups in such stereoregular polymerizations is challenging,however, due to the sensitivity of most catalysts towardsheteroatom-containing substrates. An introduction of polar and reactivegroups in the polymer backbone and into the end-groups in particular isdesirable to enhance the compatibility with polar surface, like e.g.metals or fillers and for cross-linking. Concerning an incorporationinto the polymer chain, recent work has resulted in an advance towardsstereoregular polar functionalized poly(propylene) (Nozaki et al.,Angew. Chem., Int. Ed. 2016, 55, (26), 7505-7509.) For poly(dienes),insertion polymerization of functionalized dienes and other pathways tostereoregular poly(dienes) have been reported (Leicht et al., S. ACSMacro Lett. 2016, 5, (6), 777-780; Leicht et al., Polym. Chem. 2016; Cuiet al., Polym. Chem. 2016, 7, (6), 1264-1270.) Examples for syntheses ofchain-end functionalized poly(dienes) are so far based on methods likeanionic polymerization (Quirk et al., Polymer 2004, 45, (3), 873-880;Stewart et al., British Polymer Journal 1990, 22, (4), 319-325.) or ringopening metathesis polymerization (Hillmyer et al., Macromolecules 1997,30, (4), 718-721; Ji et al., Macromolecules 2004, 37, (15), 5485-5489;Chung et al., Macromolecules 1992, 25, (20), 5137-5144) that do notprovide access to stereoregular polymers. There remains a need for amethod to produce stereoregular polymers functionalized with polargroups.

SUMMARY OF THE INVENTION

Most lanthanide-based catalyst precursors for stereoselective dienepolymerization require activation by a second reagent, oftenorgano-metal compounds. The present invention includes the usage ofpolar functionalized organo-metal activators for the synthesis ofchain-end functionalized stereoregular dienes. Further, the combinationof this method with the generation of functionalized chain-ends byquenching at the end of the polymerization and direct copolymerizationwith functionalized dienes gives access to stereoregular, trifunctional,hetero-telechelic poly(dienes).

The preparation of stereoregular poly(dienes) with functional groups inthe main chain as well as in both end-groups, the later in ahetero-telechelic fashion is disclosed. A key element is the findingthat Nd-based trans-selective systems for diene polymerization aretolerant towards different functional groups based on nitrogen orsulfur. Further, activation of Nd(BH₄)₃.(THF)₃ proceeds withfunctionalized magnesium alkyls to introduce functional groups at theinitiating chain-ends. At the terminating chain-end, an end-group couldbe generated by conversion of reactive metal-carbon bonds present in thecatalyst system with suitable quenching reagents. Notably, all threeelements are compatible with one another and can be carried outtogether, i.e. stereoregularity or the nature of the reactivemetal-polymeryl bonds are not compromised by the presence of functionalactivators or monomers.

Stereoregular poly(dienes) with three different functional groups weresynthesized by insertion polymerization. The functional groups arelocated simultaneously in the polymer backbone and at both chain ends,yielding hetero-telechelic and in-chain functionalized polymers. Acombination of three compatible functionalization methods allows for thesyntheses of these particular polymers. Nd(BH₄)₃.(THF)₃ catalyzes, afteractivation with MgR₂, the direct copolymerization of 1,3-butadiene orisoprene with polar functionalized dienes, thus enabling thefunctionalization of the polymer's backbone. The use of functionalizedorgano-Mg compounds, like (PhS—C₅H₁₀)₂Mg, for the activation ofNd(BH₄)₃.(THF)₃ enables the functionalization of one chain-end andquenching of the polymerization with suitable reagents like Si(OEt)₄allows for the functionalization of the other chain-end. Whileactivation of Nd(BH₄)₃.(THF)₃ with MgR₂ initiates usually a 1,4-transselective diene polymerization, the use of polar organo-Mg compounds asactivation reagents has also been shown to be a viable method forchain-end functionalization in cis-selective diene polymerizations.

The present invention therefore involves the use of functionalmagnesium-based chain transfer reagents that impart functionality on theend of every chain end. By combining this technique with knownfunctionalization techniques such as termination with functionalterminators or copolymerization with functional monomers, the inventiondescribes a method to make stereoregular polymers that containfunctionality on both ends, as well as in-chain. Either high-cis orhigh-trans polymers can be made through changes to the catalyst system,without affecting the functionalization reactions.

The present invention is directed to a stereoregular functionalizedelastomer represented by poly(M1 co M2), wherein the functionalizedelastomer comprises a microstructure selected from the group consistingof microstructures having at least 90 percent by weight of monomerresidues in trans 1,4-configuration, and microstructures having at least80 percent by weight of monomer residues in cis 1,4-configuration;wherein M1 is selected from the group consisting of isoprene and1,3-butadiene; and M2 is of formula 4

wherein R⁶ is a covalent bond, phenylene, a linear or branched alkanediyl group containing 1 to 10 carbon atoms, or a combination of one ormore phenylene groups and one or more linear or branched alkane diylgroups containing 1 to 10 carbon atoms; R⁷ is hydrogen or a linear orbranched alkyl group containing 1 to 10 carbon atoms; X¹ is selectedfrom formulas 5 and 6

wherein R⁸ and R⁹ are independently trialkylsilyl, phenyl or a linear orbranched alkyl group containing 1 to 10 carbon atoms, or one of R⁸ andR⁹ is hydrogen and the other is phenyl or a linear or branched alkylgroup containing 1 to 10 carbon atoms, or R⁸ and R⁹ taken together withthe nitrogen atom represent a nitrogen containing heterocyclic groupcontaining from 4 to 12 carbon atoms; and X² is a sulfur atom or astructure of formula 7 or 8

wherein when X² is of formula 8, the S atom of formula 8 is adjacent tothe phenyl ring of formula 6 and the N atom of formula 8 is adjacent toR⁶.

There is further disclosed a rubber composition comprising thefunctionalized elastomer, and a tire comprising the rubber composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows FIG. 1: ¹H NMR spectrum of a BD/3 copolymer (Table 1-A,entry 7, recorded at 27° C. in C₆D₆).

FIG. 2: ¹H NMR spectrum of a poly(isoprene) sample with triethoxysilylend-groups (Table 1, entry 5, recorded at 27° C. in C₆D₆).

FIG. 3: ¹H and 1D-TOCSY NMR spectra of a copolymer synthesized fromisoprene and comonomer 3, showing the connectivity of the butyl chainand the poly(isoprene) backbone (Table 1, entry 10, recorded at 27° C.in C₆D₆). Irradiation at 1 (250 ms mixing time) results in excitation ofsignals 2, 3, 4, 5, and even 6 by magnetization transfer through bonds,proving the attachment of the butyl moiety to the PIP-backbone.

FIG. 4: ¹H NMR spectrum and according DOSY NMR traces of chain-endfunctionalized poly(butadiene) sample. The sample was obtained by apolymerization activated with Mg-5 (Table 2, entry 8, spectra recordedat 27° C. in C₆D₆).

FIG. 5: ¹H NMR spectrum of a trifunctionalized, hetero-telechelicpoly(isoprene) sample (recorded at 27° C. in C₆D₆).

FIG. 6: ¹H NMR spectrum and according DOSY NMR traces of atrifunctionalized, hetero-telechelic poly(butadiene) sample, proving theconnection of all different functional groups to the polymer backbone(recorded at 27° C. in C₆D₆).

FIG. 7: Combination of three different methods for the introduction offunctional groups, thus enabling the synthesis of triple functionalized,hetero-telechelic poly(dienes).

DETAILED DESCRIPTION OF THE INVENTION

There is disclosed a stereoregular functionalized elastomer representedby poly(M1 co M2), wherein the functionalized elastomer comprises amicrostructure selected from the group consisting of microstructureshaving at least 90 percent by weight of monomer residues in trans1,4-configuration, and microstructures having at least 80 percent byweight of monomer residues in cis 1,4-configuration; wherein M1 isselected from the group consisting of isoprene and 1,3-butadiene; and M2is of formula 4

wherein R⁶ is a covalent bond, phenylene, a linear or branched alkanediyl group containing 1 to 10 carbon atoms, or a combination of one ormore phenylene groups and one or more linear or branched alkane diylgroups containing 1 to 10 carbon atoms; R⁷ is hydrogen or a linear orbranched alkyl group containing 1 to 10 carbon atoms; X¹ is selectedfrom formulas 5 and 6

wherein R⁸ and R⁹ are independently trialkylsilyl, phenyl or a linear orbranched alkyl group containing 1 to 10 carbon atoms, or one of R⁸ andR⁹ is hydrogen and the other is phenyl or a linear or branched alkylgroup containing 1 to 10 carbon atoms, or R⁸ and R⁹ taken together withthe nitrogen atom represent a nitrogen containing heterocyclic groupcontaining from 4 to 12 carbon atoms; and X² is a sulfur atom or astructure of formula 7 or 8

wherein when X² is of formula 8, the S atom of formula 8 is adjacent tothe phenyl ring of formula 6 and the N atom of formula 8 is adjacent toR⁶.

The functionalized elastomer is made via a polymerization utilizing alanthanide based catalyst system. Suitable catalysts include neodymiumbased catalysts, including neodymium borohydride complexes activatedwith dialkylmagnesium compounds, and neodymium carboxylates activatedwith dialkylmagnesium compounds and alkyl aluminum chlorides.

Such polymerizations are typically conducted in a hydrocarbon solventthat can be one or more aromatic, paraffinic, or cycloparaffiniccompounds. These solvents will normally contain from 4 to 10 carbonatoms per molecule and will be liquids under the conditions of thepolymerization. Some representative examples of suitable organicsolvents include pentane, isooctane, cyclohexane, normal hexane,benzene, toluene, xylene, ethylbenzene, and the like, alone or inadmixture.

In one embodiment, the neodymium catalyst system is a neodymiumborohydride activated with a functional dialkyl magnesium compound. Inone embodiment, the neodymium borohydride is Nd(BH₄)₃.(THF)₃ where THFis tetrahydrofuran. Suitable functional dialkyl magnesium compoundsincluded compound of formula 1Q-R¹—Mg—R¹-Q  1where R¹ is phenylene, or a linear or branched alkane diyl groupcontaining 2 to 10 carbon atoms, or a combination of one or morephenylene groups and one or more linear or branched alkane diyl groupscontaining 1 to 10 carbon atoms;Q is of formula 2 or I3—S—R²  2where R2 is phenyl, or a linear or branched alkyl group containing 2 to10 carbon atoms;

where R³ and R⁴ are independently phenyl or a linear or branched alkylgroup containing 1 to 10 carbon atoms, or R² and R³ taken together withthe nitrogen atom represent a nitrogen containing heterocyclic groupcontaining from 4 to 12 carbon atoms.

In one embodiment, the neodymium catalyst system used in the process ofthis invention is made by preforming three catalyst components. Thesecomponents are (1) the functional dialkyl magnesium compound of formulaI, (2) a neodymium carboxylate, and (3) an alkyl aluminum chloride. Inmaking the neodymium catalyst system the neodymium carboxylate and thealkyl aluminum chloride compound are first reacted together for 10seconds to 30 minutes in the presence of isoprene or butadiene toproduce a neodymium-aluminum catalyst component. The neodymiumcarboxylate and the organoaluminum compound are preferable reacted for 2minutes to 30 minutes and are more preferable reacted for 3 to 25minutes in producing the neodymium-aluminum catalyst component.

The neodymium-aluminum catalyst component is then reacted with thefunctional dialkyl magnesium compound to yield the active catalystsystem.

The neodymium catalyst system will typically be pre-formed at atemperature that is within the range of about 0° C. to about 100° C. Theneodymium catalyst system will more typically be prepared at atemperature that is within the range of about 10° C. to about 60° C.

The neodymium carboxylate utilizes an organic monocarboxylic acid ligandthat contains from 1 to 20 carbon atoms, such as acetic acid, propionicacid, valeric acid, hexanoic acid, 2-ethylhexanoic acid, neodecanoicacid, lauric acid, stearic acid and the like neodymium naphthenate,neodymium neodecanoate, neodymium octanoate, and other neodymium metalcomplexes with carboxylic acid containing ligands containing from 1 to20 carbon atoms.

The concentration of the total catalyst system employed of course,depends upon factors such as purity of the system, polymerization ratedesired, temperature and other factors. Therefore, specificconcentrations cannot be set forth except to say that catalytic amountsare used.

Temperatures at which the polymerization reaction is carried out can bevaried over a wide range. Usually the temperature can be varied fromextremely low temperatures such as −60° C. up to high temperatures, suchas 150° C. or higher. Thus, the temperature is not a critical factor ofthe invention. It is generally preferred, however, to conduct thereaction at a temperature in the range of from about 10° C. to about 90°C. The pressure at which the polymerization is carried out can also bevaried over a wide range. The reaction can be conducted at atmosphericpressure or, if desired, it can be carried out at sub-atmospheric orsuper-atmospheric pressure. Generally, a satisfactory polymerization isobtained when the reaction is carried out at about autogenous pressure,developed by the reactants under the operating conditions used.

Examples of useful functional dialkyl magnesium compounds of formula 1include but are not limited to compounds such as the following

The polymerization can be quenched or terminated by the addition of afunctional terminator, an alcohol or another protic source, such aswater.

In one embodiment, the polymerization is terminated using a functionalterminator. By functional terminator, it is meant an organic compoundcapable of terminating the polymerization reaction, wherein the organiccompound is substituted with a functional group comprising at least oneheteroatom selected from phosphorus, boron, oxygen, halogens andsilicon.

In one embodiment, the functional terminator comprises at least onefunctional group selected from the group consisting of phosphane,phosphonic acid, phosphate, phosphodiester, phosphotriester, silyl,alklysilyl, alkoxysilyl, and siloxy.

Useful functional terminators include but are not limited totetraethoxysilane, n-octyltriethoxysilane,3-chloropropyltriethoxysilane, and chlorodiphenylphosphine.

Suitable monomers for use in the polymerization are conjugated dienemonomers and functionalized versions thereof. Suitable conjugated dienemonomers include 1,3-butadiene and isoprene. Other suitable conjugateddiene monomers include 2,3-dimethyl-1,3-butadiene, piperylene,3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene, and the like, andcombinations thereof.

In one embodiment, the monomer includes a functionalized monomer offormula 4

wherein R⁶ is a covalent bond, phenylene, a linear or branched alkanediyl group containing 1 to 10 carbon atoms, or a combination of one ormore phenylene groups and one or more linear or branched alkane diylgroups containing 1 to 10 carbon atoms; R⁷ is hydrogen or a linear orbranched alkyl group containing 1 to 10 carbon atoms; X¹ is selectedfrom formulas 5 and 6

wherein R⁸ and R⁹ are independently trialkylsilyl, phenyl or a linear orbranched alkyl group containing 1 to 10 carbon atoms, or one of R⁸ andR⁹ is hydrogen and the other is phenyl or a linear or branched alkylgroup containing 1 to 10 carbon atoms, or R⁸ and R⁹ taken together withthe nitrogen atom represent a nitrogen containing heterocyclic groupcontaining from 4 to 12 carbon atoms; and X² is a sulfur atom or astructure of formula 7 or 8

wherein when X² is of formula 8, the S atom of formula 8 is adjacent tothe phenyl ring of formula 6 and the N atom of formula 8 is adjacent toR⁶.

In one embodiment, the nitrogen containing heterocyclic group isselected from the group consisting of the structures

wherein R⁵ groups can be the same or different and represent a memberselected from the group consisting of linear or branched alkyl groupscontaining from 1 to about 10 carbon atoms, aryl groups, allyl groups,and alkoxy groups, and wherein Y represents oxygen, sulfur, or amethylene group, and n is an integer from 4 to 12.

In one embodiment, suitable functionalized monomers are selected fromthe following monomer structures

where in monomer 3, TMS refers to a trimethylsilyl group.

The use of functional magnesium-based chain transfer reagents of formula1 imparts functionality on the end of every polymer chain end. Bycombining the technique with known functionalization techniques such astermination with functional terminators or copolymerization withfunctional monomers, the polymerization results in stereoregularpolymers that contain functionality on both ends, as well as in-chain.Either high-cis or high-trans polymers can be made through changes tothe catalyst system, without affecting the functionalization reactions.By stereoregular, it is meant that the polymer microstructure includesat least 80 percent by weight of monomer residues (i.e., polymersubunits derived from a given monomer) in the cis 1,4-configuration, or90 percent by weight of monomer residues in the trans 1,4-configuration.In one embodiment, the polymer contains at least 85 percent by weight ofmonomer residues in cis 1,4-configuration. In one embodiment, thepolymer contains at least 95 percent by weight of monomer residues intrans 1,4-configuration.

A stereoregular functionalized elastomer so produced may be representedby poly(M1 co M2), wherein the functionalized elastomer comprises amicrostructure selected from the group consisting of microstructureshaving at least 90 percent by weight of monomer residues in trans1,4-configuration, and microstructures having at least 80 percent byweight of monomer residues in cis 1,4-configuration; wherein M1 isselected from the group consisting of isoprene and 1,3-butadiene; and M2is of formula 4.

The copolymer functionalized elastomer of the invention may becompounded into a rubber composition.

The rubber composition may optionally include, in addition to thecopolymer, one or more rubbers or elastomers containing olefinicunsaturation. The phrases “rubber or elastomer containing olefinicunsaturation” or “diene based elastomer” are intended to include bothnatural rubber and its various raw and reclaim forms as well as varioussynthetic rubbers. In the description of this invention, the terms“rubber” and “elastomer” may be used interchangeably, unless otherwiseprescribed. The terms “rubber composition,” “compounded rubber” and“rubber compound” are used interchangeably to refer to rubber which hasbeen blended or mixed with various ingredients and materials and suchterms are well known to those having skill in the rubber mixing orrubber compounding art. Representative synthetic polymers are thehomopolymerization products of butadiene and its homologues andderivatives, for example, methylbutadiene, dimethylbutadiene andpentadiene as well as copolymers such as those formed from butadiene orits homologues or derivatives with other unsaturated monomers. Among thelatter are acetylenes, for example, vinyl acetylene; olefins, forexample, isobutylene, which copolymerizes with isoprene to form butylrubber; vinyl compounds, for example, acrylic acid, acrylonitrile (whichpolymerize with butadiene to form NBR), methacrylic acid and styrene,the latter compound polymerizing with butadiene to form SBR, as well asvinyl esters and various unsaturated aldehydes, ketones and ethers,e.g., acrolein, methyl isopropenyl ketone and vinylethyl ether. Specificexamples of synthetic rubbers include neoprene (polychloroprene),polybutadiene (including cis-1,4-polybutadiene), polyisoprene (includingcis-1,4-polyisoprene), butyl rubber, halobutyl rubber such aschlorobutyl rubber or bromobutyl rubber, styrene/isoprene/butadienerubber, copolymers of 1,3-butadiene or isoprene with monomers such asstyrene, acrylonitrile and methyl methacrylate, as well asethylene/propylene terpolymers, also known as ethylene/propylene/dienemonomer (EPDM), and in particular, ethylene/propylene/dicyclopentadieneterpolymers. Additional examples of rubbers which may be used includealkoxy-silyl end functionalized solution polymerized polymers (SBR, PBR,IBR and SIBR), silicon-coupled and tin-coupled star-branched polymers.The preferred rubber or elastomers are polyisoprene (natural orsynthetic), polybutadiene and SBR.

In one aspect the at least one additional rubber is preferably of atleast two of diene based rubbers. For example, a combination of two ormore rubbers is preferred such as cis 1,4-polyisoprene rubber (naturalor synthetic, although natural is preferred), 3,4-polyisoprene rubber,styrene/isoprene/butadiene rubber, emulsion and solution polymerizationderived styrene/butadiene rubbers, cis 1,4-polybutadiene rubbers andemulsion polymerization prepared butadiene/acrylonitrile copolymers.

In one aspect of this invention, an emulsion polymerization derivedstyrene/butadiene (E-SBR) might be used having a relatively conventionalstyrene content of about 20 to about 28 percent bound styrene or, forsome applications, an E-SBR having a medium to relatively high boundstyrene content, namely, a bound styrene content of about 30 to about 45percent.

By emulsion polymerization prepared E-SBR, it is meant that styrene and1,3-butadiene are copolymerized as an aqueous emulsion. Such are wellknown to those skilled in such art. The bound styrene content can vary,for example, from about 5 to about 50 percent. In one aspect, the E-SBRmay also contain acrylonitrile to form a terpolymer rubber, as E-SBAR,in amounts, for example, of about 2 to about 30 weight percent boundacrylonitrile in the terpolymer.

Emulsion polymerization prepared styrene/butadiene/acrylonitrilecopolymer rubbers containing about 2 to about 40 weight percent boundacrylonitrile in the copolymer are also contemplated as diene basedrubbers for use in this invention.

The solution polymerization prepared SBR (S—SBR) typically has a boundstyrene content in a range of about 5 to about 50, preferably about 9 toabout 36, percent. The S—SBR can be conveniently prepared, for example,by organo lithium catalyzation in the presence of an organic hydrocarbonsolvent.

In one embodiment, cis 1,4-polybutadiene rubber (BR) may be used. SuchBR can be prepared, for example, by organic solution polymerization of1,3-butadiene. The BR may be conveniently characterized, for example, byhaving at least a 90 percent cis 1,4-content.

The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber arewell known to those having skill in the rubber art.

The term “phr” as used herein, and according to conventional practice,refers to “parts by weight of a respective material per 100 parts byweight of rubber, or elastomer.”

The rubber composition may also include up to 70 phr of processing oil.Processing oil may be included in the rubber composition as extendingoil typically used to extend elastomers. Processing oil may also beincluded in the rubber composition by addition of the oil directlyduring rubber compounding. The processing oil used may include bothextending oil present in the elastomers, and process oil added duringcompounding. Suitable process oils include various oils as are known inthe art, including aromatic, paraffinic, naphthenic, vegetable oils, andlow PCA oils, such as MES, TDAE, SRAE and heavy naphthenic oils.Suitable low PCA oils include those having a polycyclic aromatic contentof less than 3 percent by weight as determined by the IP346 method.Procedures for the IP346 method may be found in Standard Methods forAnalysis & Testing of Petroleum and Related Products and BritishStandard 2000 Parts, 2003, 62nd edition, published by the Institute ofPetroleum, United Kingdom.

The rubber composition may include from about 10 to about 150 phr ofsilica. In another embodiment, from 20 to 80 phr of silica may be used.

The commonly employed siliceous pigments which may be used in the rubbercompound include conventional pyrogenic and precipitated siliceouspigments (silica). In one embodiment, precipitated silica is used. Theconventional siliceous pigments employed in this invention areprecipitated silicas such as, for example, those obtained by theacidification of a soluble silicate, e.g., sodium silicate.

Such conventional silicas might be characterized, for example, by havinga BET surface area, as measured using nitrogen gas. In one embodiment,the BET surface area may be in the range of about 40 to about 600 squaremeters per gram. In another embodiment, the BET surface area may be in arange of about 80 to about 300 square meters per gram. The BET method ofmeasuring surface area is described in the Journal of the AmericanChemical Society, Volume 60, Page 304 (1930).

The conventional silica may also be characterized by having adibutylphthalate (DBP) absorption value in a range of about 100 to about400, alternatively about 150 to about 300.

The conventional silica might be expected to have an average ultimateparticle size, for example, in the range of 0.01 to 0.05 micron asdetermined by the electron microscope, although the silica particles maybe even smaller, or possibly larger, in size.

Various commercially available silicas may be used, such as, only forexample herein, and without limitation, silicas commercially availablefrom PPG Industries under the Hi-Sil trademark with designations 210,243, etc; silicas available from Rhodia, with, for example, designationsof Z1165MP and Z165GR and silicas available from Degussa AG with, forexample, designations VN2 and VN3, etc.

Commonly employed carbon blacks can be used as a conventional filler inan amount ranging from 10 to 150 phr. In another embodiment, from 20 to80 phr of carbon black may be used. Representative examples of suchcarbon blacks include N110, N121, N134, N220, N231, N234, N242, N293,N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539,N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907,N908, N990 and N991. These carbon blacks have iodine absorptions rangingfrom 9 to 145 g/kg and DBP number ranging from 34 to 150 cm³/100 g.

Other fillers may be used in the rubber composition including, but notlimited to, particulate fillers including ultra-high molecular weightpolyethylene (UHMWPE), crosslinked particulate polymer gels includingbut not limited to those disclosed in U.S. Pat. Nos. 6,242,534;6,207,757; 6,133,364; 6,372,857; 5,395,891; or 6,127,488, andplasticized starch composite filler including but not limited to thatdisclosed in U.S. Pat. No. 5,672,639. Such other fillers may be used inan amount ranging from 1 to 30 phr.

In one embodiment, the rubber composition may contain a conventionalsulfur containing organosilicon compound. In one embodiment, the sulfurcontaining organosilicon compounds are the 3,3′-bis(trimethoxy ortriethoxy silylpropyl) polysulfides. In one embodiment, the sulfurcontaining organosilicon compounds are 3,3′-bis(triethoxysilylpropyl)disulfide and/or 3,3′-bis(triethoxysilylpropyl) tetrasulfide.

In another embodiment, suitable sulfur containing organosiliconcompounds include compounds disclosed in U.S. Pat. No. 6,608,125. In oneembodiment, the sulfur containing organosilicon compounds includes3-(octanoylthio)-1-propyltriethoxysilane,CH₃(CH₂)₆C(═O)—S—CH₂CH₂CH₂Si(OCH₂CH₃)₃, which is available commerciallyas NXT™ from Momentive Performance Materials.

In another embodiment, suitable sulfur containing organosiliconcompounds include those disclosed in U.S. Patent Publication No.2003/0130535. In one embodiment, the sulfur containing organosiliconcompound is Si-363 from Degussa.

The amount of the sulfur containing organosilicon compound in a rubbercomposition will vary depending on the level of other additives that areused. Generally speaking, the amount of the compound will range from 0.5to 20 phr. In one embodiment, the amount will range from 1 to 10 phr.

It is readily understood by those having skill in the art that therubber composition would be compounded by methods generally known in therubber compounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials suchas, for example, sulfur donors, curing aids, such as activators andretarders and processing additives, such as oils, resins includingtackifying resins and plasticizers, fillers, pigments, fatty acid, zincoxide, waxes, antioxidants and antiozonants and peptizing agents. Asknown to those skilled in the art, depending on the intended use of thesulfur vulcanizable and sulfur-vulcanized material (rubbers), theadditives mentioned above are selected and commonly used in conventionalamounts. Representative examples of sulfur donors include elementalsulfur (free sulfur), an amine disulfide, polymeric polysulfide andsulfur olefin adducts. In one embodiment, the sulfur-vulcanizing agentis elemental sulfur. The sulfur-vulcanizing agent may be used in anamount ranging from 0.5 to 8 phr, alternatively with a range of from 1.5to 6 phr. Typical amounts of tackifier resins, if used, comprise about0.5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts ofprocessing aids comprise about 1 to about 50 phr. Typical amounts ofantioxidants comprise about 1 to about 5 phr. Representativeantioxidants may be, for example, diphenyl-p-phenylenediamine andothers, such as, for example, those disclosed in The Vanderbilt RubberHandbook (1978), Pages 344 through 346. Typical amounts of antiozonantscomprise about 1 to 5 phr. Typical amounts of fatty acids, if used,which can include stearic acid comprise about 0.5 to about 3 phr.Typical amounts of zinc oxide comprise about 2 to about 5 phr. Typicalamounts of waxes comprise about 1 to about 5 phr. Often microcrystallinewaxes are used. Typical amounts of peptizers comprise about 0.1 to about1 phr. Typical peptizers may be, for example, pentachlorothiophenol anddibenzamidodiphenyl disulfide.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used, i.e., primaryaccelerator. The primary accelerator(s) may be used in total amountsranging from about 0.5 to about 4, alternatively about 0.8 to about 1.5,phr. In another embodiment, combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts, such as from about 0.05 to about 3 phr, in order toactivate and to improve the properties of the vulcanizate. Combinationsof these accelerators might be expected to produce a synergistic effecton the final properties and are somewhat better than those produced byuse of either accelerator alone. In addition, delayed actionaccelerators may be used which are not affected by normal processingtemperatures but produce a satisfactory cure at ordinary vulcanizationtemperatures. Vulcanization retarders might also be used. Suitable typesof accelerators that may be used in the present invention are amines,disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides,dithiocarbamates and xanthates. In one embodiment, the primaryaccelerator is a sulfenamide. If a second accelerator is used, thesecondary accelerator may be a guanidine, dithiocarbamate or thiuramcompound.

The mixing of the rubber composition can be accomplished by methodsknown to those having skill in the rubber mixing art. For example, theingredients are typically mixed in at least two stages, namely, at leastone non-productive stage followed by a productive mix stage. The finalcuratives including sulfur-vulcanizing agents are typically mixed in thefinal stage which is conventionally called the “productive” mix stage inwhich the mixing typically occurs at a temperature, or ultimatetemperature, lower than the mix temperature(s) than the precedingnon-productive mix stage(s). The terms “non-productive” and “productive”mix stages are well known to those having skill in the rubber mixingart. The rubber composition may be subjected to a thermomechanicalmixing step. The thermomechanical mixing step generally comprises amechanical working in a mixer or extruder for a period of time suitablein order to produce a rubber temperature between 140° C. and 190° C. Theappropriate duration of the thermomechanical working varies as afunction of the operating conditions, and the volume and nature of thecomponents. For example, the thermomechanical working may be from 1 to20 minutes.

The rubber composition may be incorporated in a variety of rubbercomponents of the tire. For example, the rubber component may be a tread(including tread cap and tread base), sidewall, apex, chafer, sidewallinsert, wirecoat or innerliner. In one embodiment, the component is atread.

The pneumatic tire of the present invention may be a race tire,passenger tire, aircraft tire, agricultural, earthmover, off-the-road,truck tire, and the like. In one embodiment, the tire is a passenger ortruck tire. The tire may also be a radial or bias.

Vulcanization of the pneumatic tire of the present invention isgenerally carried out at conventional temperatures ranging from about100° C. to 200° C. In one embodiment, the vulcanization is conducted attemperatures ranging from about 110° C. to 180° C. Any of the usualvulcanization processes may be used such as heating in a press or mold,heating with superheated steam or hot air. Such tires can be built,shaped, molded and cured by various methods which are known and will bereadily apparent to those having skill in such art.

This invention is illustrated by the following examples that are merelyfor the purpose of illustration and are not to be regarded as limitingthe scope of the invention or the manner in which it can be practiced.Unless specifically indicated otherwise, parts and percentages are givenby weight.

Example 1

Homopolymerizations of BD were performed to optimize polymerizationconditions for high stereoselectivity and to assess the influence of thediene:Nd ratio on the molecular weights and molecular weightdistributions of the obtained polymers. 5 μmol Nd(BH₄)₃.(THF)₃ wereactivated with 1 equiv. of MgBuz in the presence of different amounts ofBD in toluene (Table 1, entries 1-3). Polymerization at 60° C. for 5 hyielded in all cases highly stereoregular 1,4-trans-PBD (>95 mol %trans-units). The molecular weights of the obtained polymers are closeto the theoretically calculated molecular weights (for a polymerizationwhere only one polymer chain per Nd is formed) and increase linearlywith increasing BD:Nd ratio. Although GPC analyses indicate a bimodalmolecular weight distribution (cf. SI), all molecular weightdistributions are narrow (Mw/Mn=1.3-1.6). Hence, a controlled characterof the polymerization can be assumed. DSC analyses of the polymers gavethe typically two distinct melting points for high 1,4-trans-PBD. Notonly butadiene but also isoprene is stereoselectively polymerized. Apolymerization of isoprene in an NMR tube gives poly(isoprene) with 95%1,4-trans units (Table 1, entry 4). The narrow molecular weightdistribution and a molecular weight close to the theoretical value alsoindicate a controlled polymerization of isoprene. Having established thegeneral polymerization behavior under our conditions of the catalystsystem based on Nd(BH₄)₃.(THF)₃, three different approaches for thefunctionalization of the obtained stereoregular poly(diene) wereexplored: 1) The direct introduction of polar groups into the backboneof the polymer by insertion copolymerization of butadiene or isoprenewith polar functionalized dienes. 2) The functionalization of onechain-end by reaction of the reactive metal-carbon bond with a suitablequenching reagent. 3) The functionalization of the other chain-end byusing polar functionalized Mg-compounds.

TABLE 1 (Co)polymerizations of butadiene and isoprene catalyzed byNd(BH₄)₃•(THF)₃ activated with MgBu₂. yield comon. comon. M_(n) ^(b))1,4-trans- cat. time diene comon. [mg] incorp.^(a)) conv. [10³ g T_(m)^(c)) content^(d)) entry [μmol] [h] [mmol] [μmol] (%) [mol %] [%] mol⁻¹]M_(w)/M_(n) ^(b)) [°C.] [%] 1  5 5  4.6 BD — 202 (81) — — 43 1.3 45/9495 2  5 5  9.2 BD — 440 (89) — — 89 1.6 45/98 97 3  5 5 13.8 BD — 698(94) — — 133 1.4 46/98 95 4 20 3   2 IP — 125 (92) — — 7.7 1.5 n.d. 95 5^(f)) 60 2.5   6 IP — 330 (81) — 12 1.5 n.d. 93 6 ^(g)) 60 3   6 IP —411 (99) — 5.8 1.3 n.d. 95 Polymerization conditions:Nd(BH₄)₃•(THF)₃:MgBu₂ = 1:1, T = 60° C. in toluene ^(a))determined by¹HNMR ^(b))determined by GPC in THF vs. PS standards. ^(c))determined byDSC ^(d))determined by ¹³C NMR e) incorporation not determined becausecomonomer incorporation signals are overlapped by the polymer backbone.^(f)) quenched with 600 μmol Si(OEt)₄ ^(g)) quenched with 600 μmolPh₂PCl.

Example 2

Copolymerization with Polar Functionalized Dienes.

The functional group tolerance of Nd(BH₄)₃.(THF)₃ activated with MgR₂ indiene polymerizations was tested with comonomers 1-5 (Table 1-A, entries7-12).

Chart 1: Polar functionalized dienes used in copolymerizations withbutadiene and isoprene.

TABLE 1-A yield comon. comon. M_(n) ^(b)) 1,4-trans- cat. time dienecomon. [mg] incorp.^(a)) conv. [10³ g T_(m) ^(c)) content^(d)) entry[μmol] [h] [mmol] [μmol] (%) [mol %] [%] mol⁻¹] M_(w)/M_(n) ^(b)) [°C.][%]  7  5 5 4.6 BD 150 152 (61) 1 3.9 73 43 1.8 50/72 94  8  5 5 4.6 BD170 195 (79) 2 n.d.^(e)) n.d.^(e)) 46 1.6 48/93 94  9  5 5 4.6 BD 150222 (89) 3 3.6 99 44 3.0 47/61 94 10 60 5 6.2 IP 430 484 (92) 3 7.2 997.7 1.3 n.d. 96 11  5 5 4.6 BD  0.16 208 4 3.4 82 43 1.9 50/73 93 12  55 4.6 BD  0.15 196 5 3.3 80 47 3.0 49/71 93 Polymerization conditions:Nd(BH₄)₃•(THF)₃:MgBu₂ = 1:1, T = 60° C. in toluene ^(a))determined by¹HNMR ^(b))determined by GPC in THF vs. PS standards. ^(c))determined byDSC ^(d))determined by ¹³C NMR ^(e))incorporation not determined becausecomonomer incorporation signals are overlapped by the polymer backbone.f) quenched with 600 μmol Si(OEt)₄ g) quenched with 600 μmol Ph₂PCl.

Comparison of the copolymerizations with a BD homopolymerization underotherwise identical conditions reveals no to little adverse impact ofthe comonomer present on yield, molecular weight and stereoselectivity(e.g. Table 1, 1-A, entry 1 vs. 7). Copolymerizations with 3 and 5result in polymers with broader molecular weight distributions.Additionally, copolymers of 1 and 3 exhibit a lowered second meltingpoint. Incorporation of 1 and 3 proceeds efficiently (73% and 99%comonomer conversion) and yields copolymers with incorporations of 3.9mol % and 3.6 mol % respectively (FIG. 1). The incorporation ratio ofthe copolymer synthesized from butadiene and 2 could not be determinedunequivocally because all proton signals of the propyl side chain (mostindicative PhS—CH₂—) are overlapped by signals of the poly(butadiene)backbone (Table 1, entry 8). In contrast, the signal of thePhS—CH₂-group is shifted in copolymers with 4 and 5, allowing again fordetection and determination of the comonomer incorporation (3.4 and 3.3mol %, Table 1, entries 11 and 12). The formation of true copolymerswas, additionally to ¹H NMR experiments, undoubtedly established byextensive NMR analyses of the polymers including 1D TOCSY, 2D and DOSYexperiments.

These polymerizations prove that Nd(BH₄)₃.(THF)₃ activated with MgR₂ isa viable catalyst system for the direct copolymerization of butadiene orisoprene with functionalized dienes to polar functionalized1,4-trans-poly(dienes).

Example 3

Chain-End Functionalization by Quenching.

The second part of the functionalization strategy aims at the reactionof reactive metal-carbon bonds present with a suitable quenching reagent(Scheme 1).

We tested four different quenching reagents, Si(OEt)₄, Ph₂PCl, B(OEt)₃,and P(O)(OEt)₃ towards their reactivity with the aforementionedmetal-carbon bonds. For this purpose, polymerizations run with an IP:Ndratio of 100:1 were terminated by the addition of the quenching reagents(cf. Table 1, entries 5 and 6, for examples with Si(OEt)₄ and Ph₂PCl).The reaction mixture was stirred at the polymerization temperature untilit became colorless. The polymers were isolated by precipitation in dryacetonitrile (polymers quenched with Si(OEt)₄, B(OEt)₃, or P(O)(OEt)₃)or acidified MeOH (Ph₂PCl-modified) followed by drying under reducedpressure. To verify the functionalization by quenching, the polymerswere subjected to a thorough analysis by means of NMR spectroscopy. ¹Hand ¹³C NMR showed no indication for a successful functionalization forpolymers quenched with B(OEt)₃ or P(O)(OEt)₃. In contrast, the polymerquenched with Si(OEt)₄ exhibits characteristic shifts for anethoxy-moiety in the ¹H NMR spectrum at δ=3.89 ppm and δ=1.20 ppm (FIG.2). The assignment of these signals to a SiOCH₂CH₃ group issubstantiated by ¹H-¹³C-HSQC NMR spectroscopy revealing thecorresponding carbon shifts at δ=59.4 ppm and 17.8 ppm. A connectivityof these ethoxy moieties to the poly(isoprene) backbone was probed by 1DTOCSY and DOSY NMR spectroscopy. The formation of ethoxysilyl endgroupsis unambiguously proven by DOSY-NMR. Both, the SiOCH₂CH₃ group as wellas the backbone signals exhibit the same diffusion coefficient, i.e.both correlate to a species with a comparable molecular weight, thiswould not be the case for e.g BuSi(OEt)₃ which could likely be formedfrom the reaction of residual RMgBu with Si(OEt)₄.

A quantitative view on the end-group functionalization reveals that thereaction does not proceed quantitatively, with quenching efficiencies(i.e. portion of chains functionalized) between 40 and 50%.

A polymer quenched with Ph₂PCl at the end of the polymerization reactionexhibits characteristic ¹H NMR shifts in the aromatic region atδ=7.81-6.90 ppm, indicating a successful functionalization of thepolymer. Although this assumption is substantiated by the observation ofsignals in the ³¹P NMR spectrum, the presence of at least sevendifferent ³¹P species, however, points to a low selectivity or theoccurrence of side reactions. Still, DOSY-NMR establishes the connectionof the aromatic protons to the poly(isoprene) backbone in terms ofidentical diffusion coefficients and thus a successfulfunctionalization.

Example 4

Chain-End Functionalization by Activation with FunctionalizedMg-Reagents.

The third functionalization strategy targets the introduction offunctional groups via the use of functional activation reagents, i.e.organo-magnesium compounds. This functionalization would result inpoly(dienes) with polar end groups (Scheme 2).

Before we started to assess the potential of this approach towards apossible functionalization of the polymer chain-end, we tested ourpolymerization conditions in terms of this method's general ability totransfer organic moieties from Mg to Nd and eventually to the chain-endwith a non-functionalized alkyl group, i.e. an n-butyl moiety throughtransfer from MgBu₂. The presence of n-butyl end-groups was observed bythe appearance of a ¹H NMR signal with a shift typical for aliphatic—CH₃ groups (δ=0.90 ppm) for all polymerizations in which MgBu₂ was usedas activation reagent.

A detailed NMR analysis to prove the presence of a butyl group aschain-end was performed for a copolymer synthesized from IP and 3. TOCSYirradiation at the resonance of the CH₃ group results in magnetizationtransfer along the residual butyl chain up to the aliphatic and olefinicsignals of the first isoprene unit in the backbone (FIG. 3). Thisoutcome was further substantiated by DOSY-NMR, also showing theattachment of the butyl moiety to the PIP backbone.

Example 5

Having established the possibility to introduce a chain-end bytransferring an organic group from Mg to Nd, we engaged in the synthesisof different polar functionalized organo-Mg compounds (Chart 2).

Chart 2: Polar functionalized organo-magnesium compounds used for theactivation of Nd-based catalyst systems.

Polar functionalized organo-Mg compounds Mg-1 to Mg-5 were synthesizedby reacting the according Br- or Cl-compound, e.g. Cl—C₅H₁₀—SPh forMg-5, with activated Mg to form the mono-alkyl Mg compoundClMg—C₅H₁₀—SPh. The di-alkyl Mg compound Mg(C₅H₁₀—SPh)₂, Mg-5, was thenformed by shifting the Schlenk equilibrium towards MgR₂/MgCl₂ uponaddition of dioxane. Removal of MgX₂ gave the desired magnesiumcompounds Mg-1 to Mg-5 in good to high yields with the saturatedspecies, e.g. C₅H₁₁—SPh, as a side product. There is no need, however,to remove the saturated species because they have no adverse influenceon the intended use of the synthesized organo-Mg compounds.

Example 6

Polymerizations with a Nd:diene ratio of ca. 1:100 were performed toassess the general ability of Mg-x (x=1-5) to activate Nd(BH₄)₃.(THF)₃for the trans-selective diene polymerization. The low Nd:diene ratio waschosen to ensure an end-group to backbone ratio sufficiently high forsubsequent NMR analyses. Activation of Nd(BH₄)₃. (THF)₃ was successfulwith all different polar functionalized organo-Mg compounds. Thisincludes not only the activation by Mg-alkyl compounds (Mg-1, Mg-4, andMg-5) but also the activation by Mg-aryl compounds (Mg-2 and Mg-3).

TABLE 2 Results of diene polymerizations activated with polarfunctionalized organo-magnesium compounds. activation yield funct.groups M_(n) ^(c)) 1,4-trans- Nd diene time activation efficiency^(d))[mg] in polymer^(b)) [10³ g content^(d)) entry [μmol] [mmol] [h] reagent[%] (%) [mol %] mol^(−1]) M_(w)/M_(n) ^(c)) [%]  1 ^(e)) 60   6 IP  2.5Mg-1 94 373 (91) 1.5 10.8 3.2 93  2 20   2 IP  2.5 Mg-1 92 116 (85) 1.17.4 1.8 93  3 60   6 IP  5 Mg-2 n.d.^(f)) 324 (79) n.d.^(f)) 16.5 2.8 92 4 60   6 IP  5.5 Mg-3 42 350 (86) 0.5 18.8 4.8 91  5 50 4.6 BD  5 Mg-358 140 (56) 1.1 n.d. n.d. 94  6 50   5 IP 72 Mg-4 42 282 (83) 0.5 14.24.1 95  7 50 4.6 BD  3 Mg-4 32 106 (43) 0.8 17 2.4 93  8 50 4.6 BD  5Mg-5 92 112 (45) 2.2 5.1 1.8 94  9  5 4.6 BD  5 Mg-4 n.d.^(g)) 150 (60)n.d.^(g)) 57 2.8 95 10  5 4.6 BD  5 Mg-5 n.d.^(g)) 185 (74) n.d.^(g)) 483.0 94 Polymerization conditions: Nd(BH₄)₃•(THF)₃:MgR₂ = 1:1, T = 60° C.in toluene or C₆D₆ ^(a))activation efficiency = (funct. groups inpolymer in mol % · 100⁻¹) · (n(MgR₂) · M(diene) · m(polymer)⁻¹)⁻¹^(b))determined by ¹H NMR ^(b))determined by GPC in THF vs. PSstandards. ^(d))determined by ¹³C NMR ^(e)) Nd:MgR = 1:1.5 ^(f))notdetermined because signals of functional groups are (partially)overlapped by backbone signals ^(g))not determined because the lowamount of functional groups does not allow for a reliable integration.

¹³C-NMR shows all obtained polymers to be stereoregular with a high1,4-trans-content (91-95 mol % trans-units), comparable to the modelpolymers obtained by activation of Nd(BH₄)₃.(THF)₃ with MgBu₂. NMRexperiments verify the ability of this approach to generate polarfunctionalized chain-ends. All obtained polymers exhibit in both, ¹H and¹³C NMR, characteristic signals for the respective functional group,including pyrrolidine rings for Mg-2, Mg-3, and Mg-4, resonating betweenδ=2.94 ppm (¹³C: 47.5 ppm, Mg-2) and 2.38 ppm (¹³C: 54.1 ppm, Mg-3). Inaddition, signals for the benzylic protons of Mg-3 (¹H: 3.53 ppm, ¹³C:61.1 ppm) and (C₄H₈)N—CH₂ group of Mg-4 are found in the respectivespectra. In the case of the PhS—CH₂— group, introduced by activationwith Mg-5, a proton signal at δ=2.67 ppm (¹³C: 33.3 ppm) suggestsfunctionalization and 1D-TOCSY reveals the connectivity along theresidual pentyl-chain to the olefinic signal of the first unit in thePBD backbone. To further prove the chain-end functionalization, i.e. theattachment to the polymer chain, DOSY NMR experiments were performed forall different functional groups (FIG. 4). This verified a chain-endfunctionalization by showing that the functional groups have the samediffusion coefficients as the polymer backbone.

Chain-end functionalization proceeds efficiently for the obtainedpolymers. It is known that each activator MgR₂ transfers one moiety tothe Nd center in the activation step. Moreover, MALDI-TOF analyses ofthe obtained polymers have proved that all polymer chains bear achain-end with R-groups derived from the MgR₂ used. Under the assumptionof quantitative chain-end functionalization, it is possible to determinethe activation efficiency of the different Mg-x (Table 2). Theactivation efficiency is the ratio of the amount of functional groupsfound in the functionalized polymers to the theoretically expectedamount of functionalization expected for quantitative activation ofNd(BH₄)₃.(THF)₃, i.e.

${{activation}\mspace{14mu}{efficiency}} = \frac{{mol}\mspace{14mu}\%\mspace{14mu}\left( {{{funct}.\mspace{14mu}{groups}}\mspace{14mu}{in}\mspace{14mu}{polymer}} \right)}{{mol}\mspace{14mu}\%\mspace{14mu}\left( {{\max.\mspace{14mu}{theoret}.\mspace{14mu}{amount}}\mspace{14mu}{of}\mspace{14mu}{{funct}.\mspace{14mu}{groups}}\mspace{14mu}{in}\mspace{14mu}{polymer}} \right)}$${{with}\mspace{14mu}{mol}\mspace{14mu}\%\mspace{14mu}\left( {{\max.\mspace{14mu}{theoret}.\mspace{14mu}{amount}}\mspace{14mu}{of}\mspace{14mu}{{funct}.\mspace{14mu}{groups}}\mspace{14mu}{in}\mspace{14mu}{polymer}} \right)} = \frac{{mmol}\mspace{14mu}\left( {{Mg}\text{-}x} \right)}{{mg}\mspace{14mu}\left( {{polymer}\mspace{14mu}{yield}} \right)\text{/}{mg}\mspace{14mu}{mmol}^{- 1}\mspace{14mu}\left( {{diene}\mspace{14mu}{monomer}} \right)}$

Activation occurs moderately for Mg-3 and Mg-4 with efficiencies between42 and 58% (Mg-3) and 32 and 42% (Mg-4), respectively. In contrast,excellent activation efficiencies are observed for polymerizationsactivated with Mg-1 or Mg-5 (92-94%).

The molecular weight distributions are broader in these examples thanobserved for polymerizations activated with MgBu₂, this arises mostlikely from a slower activation compared to activation by MgBu₂ causedby the addition of Mg-x as a solid (the Mg-x used are typically poorlysoluble in toluene). Nevertheless, molecular weights comparable topolymerizations activated with MgBu₂ can be obtained by adjusting thediene:Nd ratio. Polymerizations with a diene:Nd ratio of 920:1 gavepolymers with molecular weights (48 and 57×103 g mol⁻¹) close to thetheoretical value (50×103 g mol⁻¹, Table 2, entries 9 and 10).

Example 7

We have established separately that all three methods to functionalizethe synthesized stereoregular poly(dienes) work. Further, it would behighly desirable to combine all three functionalization methods in onepolymerization. This could give access to stereoregular,hetero-telechelic poly(dienes) bearing three different functional groups(see FIG. 7).

Trifunctional Polymers.

Having established the functionalization of both end-groups and of thepolymer backbone separately, we studied the combination of all threemethods simultaneously to obtain hetero-telechelic, mid-chainfunctionalized poly(dienes).

As an example of a stereoregular poly(isoprene), the copolymerization ofIP and 3 was investigated. The polymerization was activated with Mg-1(IP:Nd:Mg=100:1:1) and quenched with Si(OEt)₄. The obtained polymer isstereoregular with 94% 1,4-trans-units. ¹H-NMR shows the presence ofTMS-groups (0.19 ppm) and TMS₂NCH₂-groups (2.84 ppm) indicating acomonomer incorporation of 2.3 mol %. CarbNCH₂-groups resonate at 3.83ppm and the aromatic protons of the carbazyl group are clearly observed(FIG. 5). The presence of 1 mol % of CarbN-groups derived from Mg-1agrees excellently for the expected theoretical degree offunctionalization (1 mol %) when quantitative chain-endfunctionalization is considered for the targeted degree ofpolymerization DP=100. 2D NMR-spectroscopy also reveals the presence of(EtO)₃Si-groups. While the proton resonance of the SiOCH₂CH₃ group isoverlapped by the resonance of CarbNCH₂-groups (3.83 ppm), the presenceof a signal at 59.0 ppm in the ¹³C dimension of the HSQC spectrum provesthe functionalization of the other chain-end. However, as alreadyobserved in the quenching experiments above, the degree offunctionalization is moderate (ca. 15-20% of the polymer chains). Theconnection of all three different functional groups to the polymerbackbones was additionally verified by DOSY NMR.

Example 8

As an example of a stereoregular poly(butadiene), a copolymerization ofBD and 6 (2 mol %) was studied. The polymerization was activated by Mg-5(BD:Nd:Mg=100:1:1) and quenched with Si(OEt)₄ at the end of thereaction. ¹H, ¹³C, and 2D NMR spectroscopy shows the polymer obtained tobe stereoregular (94% 1,4-trans-units) and reveals the presence of allthree different functional groups (FIG. 6): PhS— groups originate fromthe activation of Nd(BH₄)₃.(THF)₃ with Mg-5 (¹H: 2.66 ppm, ¹³C: 33.2 ppmfor PhS—CH₂-groups). Carbazol moieties (CarbN) introduced by directcopolymerization with 6 show characteristic shifts in the aromaticregion (e.g. ¹H: 8.04 ppm, ¹³C: 120.5 ppm) and at 3.84 ppm (¹³C: 42.5ppm) for CarbN-CH₂-groups. As already observed in the example above, themost characteristic proton resonance of the SiOCH₂CH₃ group (3.90 ppm)is (partially) overlapped by the resonance of CarbNCH₂-groups, but thepresence of SiOCH₂CH₃-groups is proven by 2D NMR spectroscopy (¹³C: 59.0ppm for SiOCH₂CH₃). A connectivity between all three differentfunctional groups and the polymer backbone was unambiguously establishedby DOSY NMR FIG. 6).

Example 9

We have shown in previous work, that the direct copolymerization offunctionalized dienes with butadiene or isoprene is feasible withcis-selective Nd-based catalyst systems. It would also be highlydesirable for these systems to introduce the possibility offunctionalizing chain-ends by activation with functionalized activators.Prior examples of the initiation of cis-selective butadienepolymerizations with magnesium alkyls are scarce. We tested the reportedcatalyst system (Nd(versatate)₃ activated with MgR₂ in the presence ofethylaluminium sesquichloride) in polymerizations of butadiene afteractivation with MgBu₂ or Mg-5. Polymerizations activated with MgBu₂showed that the used catalyst system can produce stereoregularpoly(butadiene) with a high content of 1,4-cis-units (e.g. 92 mol %).Similarly, a BD polymerization activated with Mg-5 resulted in theformation of stereoregular PBD (86 mol % 1,4-cis-units). Additionally,NMR spectroscopy reveals the presence of functional groups introduced bythe activation with Mg-5 as already described above for trans-selectivecatalyst systems. These results evidence that the introduction offunctionalized chain-ends by usage of functionalized activators is alsofeasible in cis-selective diene polymerization catalyzed by Nd-basedcatalyst systems.

What is claimed:
 1. A stereoregular functionalized elastomer representedby poly(M1 co M2), wherein the functionalized elastomer comprises amicrostructure selected from the group consisting of microstructureshaving at least 90 percent by weight of monomer residues in trans1,4-configuration, and microstructures having at least 80 percent byweight of monomer residues in cis 1,4-configuration; wherein M1 isselected from the group consisting of isoprene and 1,3-butadiene; and M2is of formula 4

wherein R⁶ is a covalent bond, phenylene, a linear or branched alkanediyl group containing 1 to 10 carbon atoms, or a combination of one ormore phenylene groups and one or more linear or branched alkane diylgroups containing 1 to 10 carbon atoms; R⁷ is hydrogen or a linear orbranched alkyl group containing 1 to 10 carbon atoms; X¹ is selectedfrom formulas 5 and 6

wherein R⁸ and R⁹ are independently phenyl or a linear or branched alkylgroup containing 1 to 10 carbon atoms, or one of R⁸ and R⁹ is hydrogenand the other is phenyl or a linear or branched alkyl group containing 1to 10 carbon atoms, or R⁸ and R⁹ taken together with the nitrogen atomrepresent a nitrogen containing heterocyclic group containing from 4 to12 carbon atoms; and X² is a sulfur atom or a structure of formula 7 or8

wherein when X² is of formula 8, the S atom of formula 8 is adjacent tothe phenyl ring of formula 6 and the N atom of formula 8 is adjacent toR⁶; wherein the elastomer comprises a terminal end comprising afunctional group selected from phosphane, phosphonic acid, phosphate,phosphodiester, phosphotriester, silyl, alkylsilyl, alkoxysilyl, andsiloxy.
 2. The stereoregular functionalized elastomer of claim 1,wherein the functionalized elastomer comprises a microstructure selectedfrom the group consisting of microstructures having at least 95 percentby weight of monomer residues in trans 1,4-configuration, andmicrostructures having at least 85 percent by weight of monomer residuesin cis 1,4-configuration.
 3. The stereoregular functionalized elastomerof claim 1, wherein the elastomer comprises a one terminal end group offormula -R¹-Q, where R¹ is phenylene, or a linear or branched alkanediyl group containing 2 to 10 carbon atoms, or a combination of one ormore phenylene groups and one or more linear or branched alkane diylgroups containing 1 to 10 carbon atoms; Q is of formula 2 or 3—S—R²  2 where R² is phenyl, or a linear or branched alkyl groupcontaining 2 to 10 carbon atoms; and

where R³ and R⁴ are independently phenyl or a linear or branched alkylgroup containing 1 to 10 carbon atoms, or R³ and R⁴ taken together withthe nitrogen atom represent a nitrogen containing heterocyclic groupcontaining from 4 to 12 carbon atoms.
 4. A rubber composition comprisingthe stereoregular functionalized elastomer of claim
 1. 5. A pneumatictire comprising the rubber composition of claim 4.